Tue 28-Feb-12 10:08 AM | edited Tue 28-Feb-12 10:31 AM by blw
You're assuming perfect conditions. In practice, the further away the subject is, the more air you have between subject and sensor. The more air you have, the more problems you'll have. Stuff like thermal disturbance, humidity, and air pollution all get between you and the subject. When you're reaching out that far, another 1000m (a kilometer!) makes a huge difference.
This kind of thing works to a degree with little brown birds (LBB), because they're not really very far away. Even at 1200mm you might be shooting them from 30m distance. That's not the situation you're describing with aircraft. Practically by definition those have to be 300m up, and that's low. More likely they are several thousand feet up, and likely not directly straight up either. That puts a km or two between you and the subject, and although the lettering is certainly a lot bigger than a LBB, the distances are far greater. Don't forget that things like thermal disturbance are not strictly airborne problems. A power plant, or even a car park can be radiating a lot of heat upwards, particularly on a sunny day. The thermals on which the raptors soar are equally the cause of problems.
In practice I doubt that even a 24mp D400 is going to get you very many more shots, if you're relying strictly on the pixel density.
> The D7000 is out for me as it's missing CAM3500
There were a LOT of aircraft photos shot with the F5 and F100, and they had only CAM900. I don't shoot aircraft, but in motorsport I'm at very much closer distances, so the angular velocity is sometimes a LOT higher. I have found that CAM3500 is only differentiable from CAM2000 in the most extreme cases, such as at 180mph and only 10-15 feet off axis. At Indianapolis Motor Speedway, I was about 100 feet off axis (up in Turn One grandstand) and I had no trouble whatsoever with CAM2000. Turn One in qualifying for the Indy 500 is about 225mph for the slow guys, and I am pretty confident that the angular velocity there is higher than for most aircraft shots, particularly if you're far enough away that you're having trouble identifying the tail number. For that matter, I shot some karts a couple of years ago at minimum range: about two feet minimum distance. (I was literally just on the other side of a guard rail.) That's probably the highest angular velocity I've ever tried. It was all I could do to pivot my body (and camera) fast enough to keep the karts in the frame, even though they were probably going only 25mph. And I got those shots with the 35-70/f2.8 AFD, on a CAM2000 body. That's hardly anyone's idea of a fast focusing lens. The other thing about aircraft is that they are extremely predictable. Unlike (say) violet-green swallows, they move in either straight lines, or curves that are easily predictable through experience. So I'd say that your aircraft can easily be shot with less sophisticated AF systems than a CAM3500. I don't think that a D7000 is going to work for the atmospheric reasons above, or for the pixel density issues as the others have said, but you shouldn't rule it out just because it doesn't have the top-of-the-line AF system.
_____ Brian... a bicoastal Nikonian and Team Member
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